“In a disturbing and dangerous trend, mass killings allegedly perpetrated by Popular Committees have at times taken on sectarian overtones,” the U.N. commission of inquiry on Syria, led by Brazilian Paulo Pinheiro, said in its latest report to the U.N. Human Rights Council in Geneva.

“Some appear to have been trained and armed by the government,” they said.

The independent investigators, who cited accounts from witnesses and victims, said people were being harassed or arrested by government-allied militia because they came from regions perceived as being supportive of the revolt.